Evaporating process and apparatus



J. MAIR I'AL EVAPORATING PROCESS AND APPARATUS Feb. 12, 1957 2 Sheng-sheet 1 Filed March 12, 1953 Feb. 12, 1957 J. MAIR ETAI.

EVAPORATING PROCESS AND APPARATUS 2 Sheets-Sheet 2 Filed March l2, 1955' 5 2 O O OO O O O OO O O Z O J. O O mNOOGOOOSO 0,000,000@ OOOOOOOO OOOOOOOO OOOOOOOO OO O OOOO O O O OO O O OOO O O OO OO O O O O O OOO O O .s M Z Z INVENTORv JA/W55 Mm BY Guy 5ms/F085 v @zu nrrafswfys United States Patent EVAPORATING PROCESS AND APPARATUS James Mair and Guy E. Sanford, Birmingham, Ala.,

assignors to Godin-Birmingham Manufacturing Company, a corporation of Alabama Application March 12, 1953, Serial No. 341,992

4 Claims. (Cl. 159-20) Our invention relates to an evaporating process and apparatus therefor, and particularly to the evaporation of liquids containing a considerable proportion of dissolved scale forming solids and has for an object the provision of ya process and apparatus in which the heat transfer between the heating medium and the liquid being evaporated is carried out under conditions in which a minimum of scale is formed.

Another object of our invention is to provide evaporating apparatus in which the liquor being evaporated is heated under pressure at a temperature lower than that at which ebullition occurs and is conveyed to a vapor head maintained at a lower pressure and temperature where the liquor dashes into vapor to the extent requiredl to provide an equilibrium between the vapor and liquor.

A further object of our invention is to provide a process and apparatus for the evaporation of scale forming liquids in which solids settling out of the solution being evaporated are periodically removed from the surfaces of the evaporator without interruption of the operation or disturbing the equilibrium conditions in the evaporator.

A still further object of our invention is to provide apparatus for the evaporation of liquors in which means are provided for heating the liquors under pressure in one part of the evaporator remote from the vapor head in which vaporization takes place, and in which a cleaning liquor is circulated through other parts ofthe evaporator, together with means to alternate the ow of liquor being evaporated and of cleaning liquor through the evaporator.

Briey our invention comprises a heating element which may be of conventional design and which is divided into sections or compartments through which liquor may be circulated selectively through fewer than all the compartments and in which a cleaning liquor is circulated through the other compartments. Suitable steam or vapor connections are provided whereby to heat the liquor being circulated. The heating element is provided with suitable piping and valves whereby the circulation of liquor to be evaporated and cleaning liquor is alternated. Any solids precipitated out of the liquor being heated are thus promptly removed. As soon as the concentration i the other in the manner to be described later.

Friice Z q contact with the heating surfaces of the heating element to become dehydrated and form hard scale. Suitable pipe connections and valve means are provided whereby the iow of cleaning fluid and liquor to be evaporated is alternated through the compartments of the heating element and the heated liquor is conveyed to the vapor head. The vapor formed in the vapor head passes to the next effect or to the condenser as is Well understood.

Apparatus embodying features of our invention is illustrated in the accompanying drawings forming a part of this application in which:

Fig. 1 is a diagrammatic view illustrating the application of our invention to a multiple effect evaporator;

Fig. 2 is a longitudinal sectional view of one form of evaporator which may be employed with our invention;

Fig. 3 is a longitudinal sectional view of the opposite end thereof;

Fig. 4 is a transverse sectional view taken along the line IV-IV of Fig. 3; and,

Fig. 5 is an end view looking in the direction ofthe arrows V-V in Fig. 3. v

Referring to the drawings for a better understanding of our invention, we show in Fig. l an evaporating system embodying by way of example three eiects indicated generally at A, B, and C. Liquor to be evaporated and heating medium is caused to pass from one effect to Each of the elects comprises a heating element 10, and a vapor head 11, remote from the heating element and disposed at a higher level, whereby to maintain therein a lower pressure and temperature. As will later appear, the tubes of the heating element 10 are at all times submerged in liquor and ebullition takes place only in the vapor head 11. Also associated with each of the heating elements 10 is a tank 12 for cleaning liquid which is circulated, in a manner to be described, through the heating element to remove deposits of solid matter precipitated out of the liquor being heated in the heating element.

Referring now to Figs. 2 to 5 inclusive we show by way of example a heating element which may be employed with our invention, though it will be apparent to those skilled in the art that many types of heating elements may be used, and others will suggest themselves to those skilled in the art which might better meet their requirements.

As shown in Figs. 2 to 5 inclusive, each heating element comprises an outer shell 13 having tube sheets 14 and 16 therein through which tubes 17 extend and are secured in place in the usual manner. The tube sheets 14 and 16 are spaced respectively from the heads 18 and 19 of the heating element. The space defined between the head 19 and the tube sheet 16 is divided by of solids in the cleaning liquor approaches that in the liquor being evaporated the cleaning liquor is added to the feed liquor. Thus, there is no loss 'of solids by reason of the use of the cleaning liquor.

Another important feature of our invention resides in the provision of a vapor head separate from the evaporator and in the maintenance of a pressure and temperature of the liquor in the heating element higher than in the vapor head and at such pressure and temperature that ebullition does not occur in the heating element but in the vapor head. We thus provide a heating element in which the heating surfaces are at all times submerged andv in which the liquor and Acleaning uid are at all times under pressure such as to prevent ebullition. Thus, such solids as calcium sulphate which may be forced out of the solution while being heated do not come in direct diametral walls 21 and 22 into four compartments 23, 24, 25 and 26. The space between the head 18 and the tube sheet 14 is divided by a vertically extending diametral wall 27 into twochambers. Pipe connections 28 and 29 afford communication with the chambers 23 and 24, and pipe connections 31 and 32 afford communication with the chambers 25 and 26. lt will be seen that by reason of the compartments just described, liquor admitted into the heating element through the pipe connection 31 passes Y through chamber 25 to the opposite end of the heating element and is returned to chamber 26 and out through pipe connection 32. Also, liquor admitted through the pipe connection 28 enters the chamber 23 and passes to the opposite end of the heating element and is returned to the chamber 24 and out through the pipe connection 29. A heating medium such as steam, or vapor, is admitted to the casing through a pipe connection 3S yand condensate is removed through a pipe connection 34.

While forward ow, backward flow, or mixed forward and backward ow as is practiced in other evaporating .sllaulsrntay be. employed withour invention, we Show for the purpose of illustratipn, and by way of example only, a forward ow system. The liquor to be evaporated it ttQdgGhdthrrOugh a'ualved pipe connection andV lzea'through a, forced; circulation pump'. 37 selectively, Q ik@ pilfmlnctions 28 and' 31. VValves, 38 and 32 lrqdaqieans. whereby the doni may bev divertedv selectively to, eitlrer of said pipe connections. The liquid' is heated in the hfeiingvelement 1 0 andis returned through thelpinegconnections'. or'32as the case'may'be. The BPQS: 2Q and V2:2 Vconnectto a pipe 33 which leads upwardly,- to., the vapor head 11. VYalves. 41 and 42 in the PPQS, Z9; and@ 32; provide means wherebyY the liquid may be directed, selectively, from thelcornpartments of the heating.; element 10, to the vapor head 11.7

Thetanli'lmay- Containv water, initially, or a solution 'etfectgiye todissolve and remove. solids deposited in the heating element 1i). Theftank12 is.,preferably located, as shown, :at a lerel above that ofV the heating element. Connected to the tank 12 is an outlet pipe 43..w.hi'ch leads Y tothe-inletfside of .a forced circulationlpurnp 44iwhich discharges through a pipe 46 and through pipes 47 and 4B which connect' respectivelywith the inlet pipe connections 28 and 3l of the heating elementV 16. Valves 49 and 51 provide means whereby the cleaning liquidl may Jbe passer/dl alternately and selectively through thepipes V28 andfS-l.; Return pipes 52 and' 53 are connected, respectively, to the. return pipes 29 and 32 from the heating element 10, and are provided respectively with valves 54 and 5.6. whereby cleaning liquid may be returned selectively to the tank 12. Y

It will be seen that by closing the valve 38 and openingY the valve 49 and closing the'valve Hand opening the value 5.6, that cleaning liquid Vmay be forced into Vthe heating element 10. through the pipe connection 28 and outY through the pipe connection Ziand returned to the tank 12. Also, byclosing the valve 39 and opening the valve'il and closing the valve 42 and opening the valve '4, cleaning liquid can be forced through the other compartments lof the heating element 10. In accordance with our invention, it is contemplated that the valves described provide 'rstfor the circulation of the liquor being heated through one 'side ofthe heating element while cleaning liquid'is being circulated through the other. lt is also contemplated that the valves described may be operated by any timed mechanical means known in the art to alternate the iiow of liquor and cleaning liquid, but` which for-ms no part of our invention.

The liquor after being heated passes selectively from the separate compartments of the heating element upwardly to the vapor head 11. in the carrying out of our improved process, it is contemplated that the liquor shall beiheated vintheV heating elements ofthe separate effects to temperatures just short of that at which ebullition occurs at -the'prressure prevailing in the heating element.

The pressure Vis maintained inthe separate heatingV ele` mentsby means of theforced circulating pumps 37 and 'by' reason of the fact that the vapor heads 11 are disposed at a higher level than the heating elements. Accordingly, Awhen theheated liquor passes upwardly'into the vaporhead, aportion hashes intovapor and theV remainder passes Ydownvva'rdly through a pipe 57 to which the liquor feed 55 is connected and' which leads to the inlet side of the .pump 37 Vapor formed in the vapor head il passes ,through a pipe 58 to the heating element l0 of eieet B.

arenoso 4 Y condenser 62.. The Ylinall-y concentrated liquor may be discharged through a valve 63 at the lower end of the pipe 33 in effect C.

From the foregoing it will be apparent that wehave provided a process and apparatus for the evaporation' of scale forming liquids in whichY =the liquids are heated'in a zone remote from and at a higher pressure than that in which ebullition occurs, whereby solidsV settling out of the solution being evaporated do not ,come in .dimi oontact with the heating'elements of the evaporatorv sothat Y they become dehydrated and form a hardscale, butiare carried in suspension in thev liquid, Furthermore, it will i the cleaning solution approaches that, or approximatesV that 4of Vthe liquor feed, that, instead of returning the clean-ing solutionvto the tankV 412, it will be added esto the liquor feed, for'rexample, by opening the valve 41 or 42,'V as the case maybe, instead of returning the solution to thetanle 12,. Additional' cleaning solution may be added to thetank-12 through a pipe connection 64.

While we have shown our invention in but one form, it will'be obvious to those skilled in the art that it is not vso limited, but is susceptible of` various changes and modicatins without departing from the spiritthereof, and we desire, therefore',` that only such limitations shallbe placed thereupon as are specifically set forth in the appended claims.

What we claim is:

l'. vThe Ymethod of evaporating liquid which comprises maintaining a closed system circulating supplyof cleaning liquidsepar'ate from the liquid to be evaporated, passing liquidk to*l bev evaporated and the cleaning liquid simultaneously in separate parallel paths through one zone in heat transfer relation vwith a heating medium therein maintained in a path separate from bothA the liquid to Vbe evaporated andthe cleaning liquid and heating the liquid to be evaporated therein under pressure to a temperature justbelov/` that at which ebullition occurs, regularly interchanging the liquid whereby after interchange each liquid' flows inthe path formerly occupied by the other liquid before interchange, conveying the heated liquid to be evaporated `to another 4zone remote from the heating medium which Zone is maintained at a pressure below that at'which ebullition occurs in the heated liquid, and recirculating the cleaning liquid iu the said closed system- 2- in au evaporator System including a heating element having a plurality ot compartments, means for Passing liquor to beeverforated in indirect heat neuster, rfelatio with .heating vapor selectively through Some ofthe oompartments'; nieansto maiutainthe liquor under pressur suflieient to Prevert its ebullitiou iu the .heating eleulut; means to circulate cleaning liquid simultaneously land selectively through others o fk said compartments separate from both, the liquor being evaporated and the heating vapor, and a, vapor head'separate from the heating element disposed to provide for the ebullition of the liquor therein and the separation of vapor from the liquor.

3. In an'evaporating assembly, a heating element hav: ing a ohuaberV at each end. divided into compartments with Ytubes connecting the compartments for the circula-` tion` of liquid therethrough in indirect heat transfer reletion with a heating medium, means to circulate a liquid to be evaporated through some of the compartments and tubestassociated therewith, means to circulate a cleaning liquid simultaneously through'the other compartments and tubes associated therewith separate from both the liquid to be evaporated and the heating medium, valve means for interchanging the ilorwrof liquid to be evaporated aud Cleuug :liquid through Said compartments@ vapor head remote'from said heating element, and means for passing liquid to be evaporated from the heating element to said vapor head.

4. In an evaporating assembly, a heating element having a chamber at each end divided into compartments and with tubes connecting the compartments for the circulation of liquid therethrough in indirect heat transfer relation with a heating medium, means to circulate a liquid to be evaporated through some of the compartments and tubes in a flow path always separate from the heating medium associated therewith, means to circulate a cleaning liquid simultaneously through the other compartments and tubes associated therewith and always separate from both the heating medium and the liquid to be evap orated, Valve means for interchanging the ow of liquor to be evaporated and cleaning liquid through said compartments, a vapor head remote Ifrom said heating element, means for passing liquor to be evaporated from the heating element to said vapor head, said vapor head being disposed to provide for flashing a part of the liquor to be evaporated whereby to maintain a lower pressure in the vapor head than in the heating element.

References Cited in the le of this patent UNTTED STATES PATENTS 521,974 Cooper June 26, 1894 936,760 Childs Oct. 12, 1909 1,006,197 Frasch Oct. 17, 1911 1,123,201 Almiral Dec. 29, 1914 1,870,096 Claude Aug. 2, 1932 2,576,843 Lockman Nov. 27, 1951 2,647,570 Lockman Aug. 4, 1953 

